1. Field of the Invention
This invention relates to control of planetary gearing for changing the speed and torque ratios thereof and more particularly to a new and improved double acting brake band and controls to improve operation of the band in changing gear ratios in which torque reversals are imparted to the reaction or control member of the planetary gear set.
2. Description of Related Art
Prior to the present invention various arrangements have been devised and disclosed to control the flow of power through gearing in automotive and other power transmissions. In U.S. Pat. No. 4,915,204 issued Apr. 10, 1990 to J. R. Klotz et al for Push/Pull Clutch Apply Piston Of An Automatic Transmission assigned to the assignee of this invention and hereby incorporated reference, a clutch apply piston with a single pressure plate is pushed in one direction for applying a first clutch assembly and pulled in an opposite direction for applying a second clutch assembly for establishing different ratios in an automotive power transmission. In U.S. Pat. No. 5,711,403 issued Jan. 27, 1998 to Sparks et al for a Rapid Apply Servo for a Brake Band of an Automatic Transmission, a hydraulically actuated piston is employed to operate a special brake band to frictionally engage and release a drum operatively connected to a control member of a planetary gear set to effect a ratio change.
While these prior art disclosures have various constructions for controlling the gearing of planetary transmissions and establishing ratio changes they do not disclose or suggest a double acting friction band with improved engagement and control of a reaction member of a planetary gear set subject to torque reversals when different ratios are selected as set forth in the present invention.